Gel comprising a phase-change material, method of preparing the gel, thermal exchange implement comprising the gel, and method of preparing the thermal exchange implement

ABSTRACT

Gel including a phase-change material and a gelling agent. In one embodiment, the phase-change material may be n-tetradecane, n-hexadecane or mixtures thereof. The gelling agent may be a high molecular weight styrene-ethylene-butylene-styrene (SEBS) triblock copolymer with a styrene:rubber ratio of about 30:70 to 33:67% by weight. To form the gel, the phase-change material and the gelling agent may be mixed at an elevated temperature relative to room temperature to partially, but not completely, dissolve the gelling agent. The mixture may then be cooled to room temperature. Alternatively, the phase-change material and the gelling agent may be mixed at room temperature, and the mixture may then be heated to form a viscoelastic liquid, which is then cooled to room temperature. The invention is also directed at a method of preparing the gel, a thermal exchange implement including the gel, and a method of preparing the thermal exchange implement.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 14/225,589, inventors Richard M. Formato et al., filed Mar. 26,2014, which, in turn, is a continuation-in-part of U.S. patentapplication Ser. No. 14/036,497, inventors Richard M. Formato, filedSep. 25, 2013, now U.S. Pat. No. 9,556,373, which, in turn, claims thebenefit under 35 U.S.C. 119(e) of U.S. Provisional Patent ApplicationNo. 61/705,293, filed Sep. 25, 2012, the disclosures of all of theforegoing being incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to phase-change materials andrelates more particularly to a novel gel comprising a phase-changematerial, to a method of preparing the gel, to a thermal exchangeimplement comprising the gel, and to a method of preparing the thermalexchange implement.

It is often desirable to store and/or to transport temperature-sensitivematerials, examples of such temperature-sensitive materials including,but not being limited to, pharmaceuticals, biological samples, foods,and beverages. Packaging systems for storing and/or transporting suchmaterials typically include some means for maintaining thetemperature-sensitive materials within a desired temperature range. Inmany instances, the means for maintaining the temperature-sensitivematerial within a desired temperature range includes positioning aphase-change material within the storage system in proximity to thetemperature-sensitive material. Typically, the phase-change material isselected such that it has a phase change temperature that is within thedesired temperature range for the temperature-sensitive material inquestion. A common phase-change material is water, which is typicallythickened or incorporated into some form of a gel for theabove-described type of application. Other common phase-change materialsinclude organic compounds, such as n-alkanes (e.g., n-tetradecane,n-hexadecane, and n-octadecane), fatty acid esters (e.g., methyl esters,such as lauric acid methyl ester (also known as methyl laurate) andmyristic acid methyl ester (also known as methyl myristate)), fattyalcohols (e.g., decyl alcohol (also known as 1-decanol) and dodecylalcohol (also known as 1-dodecanol)), and fatty acids (e.g., ricinoleicacid and caprylic acid).

Because phase-change materials are designed to be changeable to or froma liquid state, such phase-change materials are typically encased withinsome form of closed container. An example of one common type of closedcontainer is a flexible pouch, and an example of another common type ofclosed container is a rigid bottle.

One problem that has been encountered, particularly with organicphase-change materials like n-tetradecane is that, because suchphase-change materials have very low surface tension, if there is adefect, such as a hole, in the container holding the phase-changematerial, the phase-change material tends to pass very easily throughthe defect and subsequently flows near or onto the temperature-sensitivematerial. As can readily be appreciated, the passage of the phase-changematerial through such a defect is undesirable. Moreover, in thoseinstances where the container or portions thereof are permeable to thephase-change material (such as where the phase-change material isn-tetradecane and the container for the phase-change material is apolyethylene bottle or a pouch having polyethylene seals), thephase-change material has a tendency, over time, to permeate through thecontainer. Consequently, the phase-change material may “leak” from thecontainer even in the absence of a defect in the container.

Documents of interest may include the following, all of which areincorporated herein by reference: U.S. Pat. No. 7,964,664 B2, inventorPearce, issued Jun. 21, 2011; U.S. Pat. No. 7,919,163 B2, inventorRomero, issued Apr. 5, 2011; U.S. Pat. No. 7,714,081 B2, inventors Seraet al., issued May 11, 2010; U.S. Pat. No. 7,625,967 B2, inventor St.Clair, issued Dec. 1, 2009; U.S. Pat. No. 7,320,770 B2, inventorsChomard et al., issued Jan. 22, 2008; U.S. Pat. No. 7,294,374 B2,inventor Romero, issued Nov. 13, 2007; U.S. Pat. No. 7,105,104 B2,inventors Chomard et al., issued Sep. 12, 2006; U.S. Pat. No. 6,574,971B2, inventor Suppes, issued Jun. 10, 2003; U.S. Pat. No. 6,340,467 B1,inventor Morrison, issued Jan. 22, 2002; U.S. Pat. No. 5,994,450;inventor Pearce, issued Nov. 30, 1999; U.S. Pat. No. 5,718,835,inventors Momose et al., issued Feb. 17, 1998; U.S. Pat. No. 5,508,334,inventor Chen, issued Apr. 16, 1996; U.S. Pat. No. 5,390,791, inventorYeager, issued Feb. 21, 1995; U.S. Pat. No. 4,797,160, inventor Salyer,issued Jan. 10, 1989; U.S. Pat. No. RE 34,880, inventor Salyer, issuedMar. 21, 1995; U.S. Patent Application Publication No. US 2011/0281485A1, inventors Rolland et al., published Nov. 17, 2011; U.S. PatentApplication Publication No. US 2011/0248208 A1, inventors Rolland etal., published Oct. 13, 2011; PCT International Publication No. WO2007/040395 A1, published Apr. 12, 2007; PCT International PublicationNo. WO 03/057795 A1, published Jul. 17, 2003; European PatentApplication Publication No. EP 2,261,297 A2, published Dec. 15, 2010;and European Patent Application Publication No. EP 1,838,802 A2,published Oct. 3, 2007.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a novel gelcomprising a phase-change material.

According to one aspect of the invention, a novel gel is provided, thegel comprising a phase-change material and a gelling agent, the gelbeing formed by (a) mixing the phase-change material and the gellingagent at an intermediate temperature that is above room temperature butis below the flash point of the phase-change material and at which thegelling agent partially, but not completely, dissolves in thephase-change material, whereby a non-homogeneous mixture is produced,and (b) then, cooling the non-homogeneous mixture to room temperature.

For purposes of the present specification and claims, the expression“room temperature” may refer more broadly to a temperature in the rangeof about 15° C. to about 30° C. or may refer more specifically to atemperature in the range of about 19° C. to about 25° C.

For purposes of the present specification and claims, the expression“the flash point of the phase-change material” is defined to mean thelowest temperature at which the phase-change material, while in a liquidstate, can vaporize to form an ignitable mixture in air.

According to a detailed feature of the invention, the phase-changematerial may be at least one organic phase-change material.

According to another detailed feature of the invention, the at least oneorganic phase-change material may be at least one compound selected fromthe group consisting of n-alkanes, fatty acid esters, fatty alcohols,and fatty acids.

According to another detailed feature of the invention, the at least oneorganic phase-change material may be one or more compounds selected fromthe group consisting of n-tetradecane, n-hexadecane, n-octadecane, andmixtures thereof.

According to another detailed feature of the invention, the gellingagent may be at least one saturated olefin rubber.

According to another detailed feature of the invention, the gellingagent may be at least one hydrogenated styrenic block copolymer.

According to another detailed feature of the invention, the gellingagent may be at least one styrene-ethylene-butylene-styrene (SEBS)tri-block copolymer.

According to another detailed feature of the invention, the gellingagent may be at least one high molecular weightstyrene-ethylene-butylene-styrene tri-block copolymer with astyrene:rubber ratio in the range of about 30:70 to 33:67% by weight.

According to another detailed feature of the invention, the phase-changematerial may be n-tetradecane, and the gelling agent may be a highmolecular weight styrene-ethylene-butylene-styrene tri-block copolymerwith a styrene:rubber ratio in the range of about 30:70 to 33:67% byweight.

According to another detailed feature of the invention, the gellingagent may constitute up to about 10%, by weight, of the gel, preferablyless than 6%, by weight, of the gel, with the phase-change materialconstituting the remainder of the gel.

According to another detailed feature of the invention, the temperatureat which the phase-change material and the gelling agent are mixedtogether may be in the range of about 40° C. to about 55° C.

According to another detailed feature of the invention, the gellingagent may be at least one styrene-ethylene-propylene-styrene (SEPS)tri-block copolymer.

According to another detailed feature of the invention, the gellingagent may be at least one high molecular weightstyrene-ethylene-propylene-styrene tri-block copolymer with astyrene:rubber ratio in the range of about 20:80% by weight.

For purposes of the present specification and claims, the term “highmolecular weight,” when used to characterize SEBS and/or SEPScopolymers, may be inferred by a Brookfield viscosity of at least 400centipoise for a 10% by weight solution of [neat] polymer in toluenemeasured at 25° C. to 30° C.

According to another aspect of the invention, a novel gel is provided,the gel comprising a phase-change material and a gelling agent, the gelbeing formed by (a) mixing the phase-change material and the gellingagent at a first temperature at which the phase-change material is in aliquid state and which is below the flash point of the phase-changematerial and at which the mixture is not a viscoelastic liquid, wherebya non-homogenous mixture is produced; (b) then, heating thenon-homogeneous mixture to a second temperature that is below the flashpoint of the phase-change material and at which a viscoelastic liquid isformed; and (c) then, cooling the viscoelastic liquid to roomtemperature.

According to a detailed feature of the invention, the phase-changematerial may be at least one organic phase-change material.

According to another detailed feature of the invention, the at least oneorganic phase-change material may be at least one compound selected fromthe group consisting of n-alkanes, fatty acid esters, fatty alcohols,and fatty acids.

According to another detailed feature of the invention, the at least oneorganic phase-change material may be one or more compounds selected fromthe group consisting of n-tetradecane, n-hexadecane, n-octadecane, andmixtures thereof.

According to another detailed feature of the invention, the gellingagent may be at least one saturated olefin rubber.

According to another detailed feature of the invention, the gellingagent may be at least one hydrogenated styrenic block copolymer.

According to another detailed feature of the invention, the gellingagent may be at least one styrene-ethylene-butylene-styrene (SEBS)tri-block copolymer.

According to another detailed feature of the invention, the gellingagent may be at least one high molecular weightstyrene-ethylene-butylene-styrene tri-block copolymer with astyrene:rubber ratio in the range of about 30:70 to 33:67% by weight.

According to another detailed feature of the invention, the phase-changematerial may be n-hexadecane, and the gelling agent may be a highmolecular weight styrene-ethylene-butylene-styrene tri-block copolymerwith a styrene:rubber ratio in the range of about 30:70 to 33:67% byweight.

According to another detailed feature of the invention, the phase-changematerial may be a mixture of n-tetradecane and n-hexadecane, and thegelling agent may be a high molecular weightstyrene-ethylene-butylene-styrene tri-block copolymer with astyrene:rubber ratio in the range of about 30:70 to 33:67% by weight.

According to another detailed feature of the invention, the gellingagent may constitute up to about 10%, by weight, of the gel, preferablyless than 6%, by weight, of the gel, with the phase-change materialconstituting the remainder of the gel.

According to another detailed feature of the invention, the gellingagent may be at least one styrene-ethylene-propylene-styrene (SEPS)tri-block copolymer.

According to another detailed feature of the invention, the gellingagent may be at least one high molecular weightstyrene-ethylene-propylene-styrene tri-block copolymer with astyrene:rubber ratio in the range of about 20:80% by weight.

According to another detailed feature of the invention, where thephase-change material is a liquid at room temperature, theabove-described step of mixing the phase-change material and the gellingagent at a first temperature may take place at room temperature, i.e.,at a temperature in the range of about 15° C. to about 30° C. or, morespecifically, at a temperature in the range of about 19° C. to about 25°C.

According to another detailed feature of the invention, after the mixingstep and before the heating step, the non-homogeneous mixture may beallowed to rest for a period of time, during which time the gellingagent may swell.

According to another detailed feature of the invention, the restingperiod may be in the range of about 30 minutes to about 72 hours andpreferably may be in the range of about 16 hours to 20 hours.

According to another detailed feature of the invention, after thephase-change material and the gelling agent have been mixed to form anon-homogeneous mixture, the non-homogeneous mixture may be placed in athermal exchange implement container, and the heating, cooling andoptional resting steps may thereafter be performed on thenon-homogeneous mixture while within the thermal exchange implementcontainer.

According to another detailed feature of the invention, the temperatureat which the viscoelastic liquid is formed may be between about 40° C.and about 80° C., preferably between about 45° C. and about 65° C.

According to another detailed feature of the invention, the step ofheating the non-homogeneous mixture from the first temperature to thesecond temperature may comprise a ramp phase in which the temperature isgradually raised from the first temperature to the second temperatureand a constant (or soak) phase in which the temperature is maintained atthe second temperature.

According to another detailed feature of the invention, the ramp phasemay range from a minimum ramp rate of about 0.025° C./minute to amaximum ramp rate of about 2.5° C./minute, with a preferred ramp ratebeing in the range of about 0.15° C./minute to about 0.30° C./minute.

According to another detailed feature of the invention, the constant (orsoak) phase may range from a minimum of about 0.5 hours to a maximum ofabout 20 hours, with a preferred range of about 6 hours to about 16hours.

According to another detailed feature of the invention, the step ofcooling the viscoelastic liquid to room temperature may take placesimply by allowing the viscoelastic liquid to cool at room temperatureor may take place using cooling materials and/or equipment.

According to another detailed feature of the invention, the cooling stepmay be performed with cooling equipment and may involve a ramping downof temperature at a rate complementary to that described above for theramp phase of the heating step. In other words, the ramping down oftemperature during the cooling step may range from a minimum ramp downrate of about 0.025° C./minute to a maximum ramp down rate of about 2.5°C./minute, with a preferred ramp down rate being in the range of about0.15° C./minute to about 0.30° C./minute.

It is another object of the present invention to provide a novel methodof preparing a gel comprising a phase-change material.

According to one aspect of the invention, a novel method of preparing agel is provided, the method comprising the steps of (a) providing aphase-change material; (b) providing a gelling agent; (c) mixing thephase-change material and the gelling agent at an intermediatetemperature that is above room temperature but is below the flash pointof the phase-change material and at which the gelling agent partially,but not completely, dissolves in the phase-change material, whereby anon-homogeneous mixture is produced; and (d) then, cooling thenon-homogeneous mixture to room temperature.

According to a detailed feature of the invention, the phase-changematerial may be at least one organic phase-change material.

According to another detailed feature of the invention, the at least oneorganic phase-change material may be at least one compound selected fromthe group consisting of n-alkanes, fatty acid esters, fatty alcohols,and fatty acids.

According to another detailed feature of the invention, the at least oneorganic phase-change material may be one or more compounds selected fromthe group consisting of n-tetradecane, n-hexadecane, n-octadecane, andmixtures thereof.

According to another detailed feature of the invention, the gellingagent may be at least one saturated olefin rubber.

According to another detailed feature of the invention, the gellingagent may be at least one hydrogenated styrenic block copolymer.

According to another detailed feature of the invention, the gellingagent may be at least one styrene-ethylene-butylene-styrene tri-blockcopolymer.

According to another detailed feature of the invention, the gellingagent may be at least one high molecular weightstyrene-ethylene-butylene-styrene tri-block copolymer with astyrene:rubber ratio in the range of about 30:70 to 33:67% by weight.

According to another detailed feature of the invention, the phase-changematerial may be n-tetradecane, and the gelling agent may be a highmolecular weight styrene-ethylene-butylene-styrene tri-block copolymerwith a styrene:rubber ratio in the range of about 30:70 to 33:67% byweight.

According to another detailed feature of the invention, the gellingagent may constitute up to about 10%, by weight, of the gel, preferablyless than 6%, by weight, of the gel, with the phase-change materialconstituting the remainder of the gel.

According to another detailed feature of the invention, the temperatureat which the phase-change material and the gelling agent are mixedtogether may be in the range of about 40° C. to about 55° C.

According to another detailed feature of the invention, the gellingagent may be at least one styrene-ethylene-propylene-styrene tri-blockcopolymer.

According to another detailed feature of the invention, the gellingagent may be at least one high molecular weightstyrene-ethylene-propylene-styrene tri-block copolymer with astyrene:rubber ratio in the range of about 20:80% by weight.

According to another aspect of the invention, a novel method ofpreparing a gel is provided, the method comprising the steps of (a)providing a phase-change material; (b) providing a gelling agent; (c)mixing the phase-change material and the gelling agent at a firsttemperature at which the phase-change material is in a liquid state andwhich is below the flash point of the phase-change material and at whichthe mixture is not a viscoelastic liquid, whereby a non-homogenousmixture is produced; (d) then, heating the non-homogeneous mixture to asecond temperature that is below the flash point of the phase-changematerial and at which a viscoelastic liquid is formed; and (e) then,cooling the viscoelastic liquid to room temperature.

According to a detailed feature of the invention, the phase-changematerial may be at least one organic phase-change material.

According to another detailed feature of the invention, the at least oneorganic phase-change material may be at least one compound selected fromthe group consisting of n-alkanes, fatty acid esters, fatty alcohols,and fatty acids.

According to another detailed feature of the invention, the at least oneorganic phase-change material may be one or more compounds selected fromthe group consisting of n-tetradecane, n-hexadecane, n-octadecane, andmixtures thereof.

According to another detailed feature of the invention, the gellingagent may be at least one saturated olefin rubber.

According to another detailed feature of the invention, the gellingagent may be at least one hydrogenated styrenic block copolymer.

According to another detailed feature of the invention, the gellingagent may be at least one styrene-ethylene-butylene-styrene tri-blockcopolymer.

According to another detailed feature of the invention, the gellingagent may be at least one high molecular weightstyrene-ethylene-butylene-styrene tri-block copolymer with astyrene:rubber ratio in the range of about 30:70 to 33:67% by weight.

According to another detailed feature of the invention, the phase-changematerial may be n-hexadecane, and the gelling agent may be a highmolecular weight styrene-ethylene-butylene-styrene tri-block copolymerwith a styrene:rubber ratio in the range of about 30:70 to 33:67% byweight.

According to another detailed feature of the invention, the phase-changematerial may be a mixture of n-tetradecane and n-hexadecane, and thegelling agent may be a high molecular weightstyrene-ethylene-butylene-styrene tri-block copolymer with astyrene:rubber ratio in the range of about 30:70 to 33:67% by weight.

According to another detailed feature of the invention, the gellingagent may constitute up to about 10%, by weight, of the gel, preferablyless than 6%, by weight, of the gel, with the phase-change materialconstituting the remainder of the gel.

According to another detailed feature of the invention, the gellingagent may be at least one styrene-ethylene-propylene-styrene tri-blockcopolymer.

According to another detailed feature of the invention, the gellingagent may be at least one high molecular weightstyrene-ethylene-propylene-styrene tri-block copolymer with astyrene:rubber ratio in the range of about 20:80% by weight.

According to another detailed feature of the invention, where thephase-change material is a liquid at room temperature, theabove-described step of mixing the phase-change material and the gellingagent at a first temperature may take place at room temperature, i.e.,at a temperature in the range of about 15° C. to about 30° C. or, morespecifically, at a temperature in the range of about 19° C. to about 25°C.

According to another detailed feature of the invention, after the mixingstep and before the heating step, the non-homogeneous mixture may beallowed to rest for a period of time, during which time the gellingagent may swell.

According to another detailed feature of the invention, the restingperiod may be in the range of about 30 minutes to about 72 hours andpreferably may be in the range of about 16 hours to 20 hours.

According to another detailed feature of the invention, after thephase-change material and the gelling agent have been mixed to form anon-homogeneous mixture, the non-homogeneous mixture may be placed in athermal exchange implement container, and the heating, cooling andoptional resting steps may thereafter be performed on thenon-homogeneous mixture while within the thermal exchange implementcontainer.

According to another detailed feature of the invention, the temperatureat which the viscoelastic liquid is formed may be between about 40° C.and about 80° C., preferably between about 45° C. and about 65° C., andthe heating step may comprise heating to a temperature between about 40°C. and about 80° C., preferably between about 45° C. and about 65° C.

According to another detailed feature of the invention, the step ofheating the non-homogeneous mixture from the first temperature to thesecond temperature may comprise a ramp phase in which the temperature isgradually raised from the first temperature to the second temperatureand a constant (or soak) phase in which the temperature is maintained atthe second temperature.

According to another detailed feature of the invention, the ramp phasemay range from a minimum ramp rate of about 0.025° C./minute to amaximum ramp rate of about 2.5° C./minute, with a preferred ramp ratebeing in the range of about 0.15° C./minute to about 0.30° C./minute.

According to another detailed feature of the invention, the constant (orsoak) phase may range from a minimum of about 0.5 hours to a maximum ofabout 20 hours, with a preferred range of about 6 hours to about 16hours.

According to another detailed feature of the invention, the step ofcooling the viscoelastic liquid to room temperature may take placesimply by allowing the viscoelastic liquid to cool at room temperatureor may take place using cooling materials and/or equipment.

According to another detailed feature of the invention, the cooling stepmay be performed with cooling equipment and may involve a ramping downof temperature at a rate complementary to that described above for theramp phase of the heating step. In other words, the ramping down oftemperature during the cooling step may range from a minimum ramp downrate of about 0.025° C./minute to a maximum ramp down rate of about 2.5°C./minute, with a preferred ramp down rate being in the range of about0.15° C./minute to about 0.30° C./minute.

It is still another object to provide a novel thermal exchangeimplement.

According to one aspect of the invention, a novel thermal exchangeimplement is provided, the thermal exchange implement comprising a gelof any of the types described above and a container holding a quantityof the gel.

According to a detailed feature of the invention, the container may be aflexible pouch.

According to another detailed feature of the invention, the containermay be a rigid bottle.

It is a further object to provide a novel method for preparing a thermalexchange implement.

According to one aspect of the invention, a novel method of preparing athermal exchange implement is provided, the method comprising the stepsof (a) providing a phase-change material; (b) providing a gelling agent;(c) mixing together the phase-change material and the gelling agent atan intermediate temperature that is above room temperature but is belowthe flash point of the phase-change material and at which the gellingagent partially, but not completely, dissolves in the phase-changematerial, whereby a non-homogeneous mixture is produced; (d) then,cooling the non-homogeneous mixture to room temperature, whereby a gelis formed; and (e) depositing the gel in a thermal exchange implementcontainer.

According to a detailed feature of the invention, the phase-changematerial may be at least one organic phase-change material.

According to another detailed feature of the invention, the at least oneorganic phase-change material may be at least one compound selected fromthe group consisting of n-alkanes, fatty acid esters, fatty alcohols,and fatty acids.

According to another detailed feature of the invention, the at least oneorganic phase-change material may be one or more compounds selected fromthe group consisting of n-tetradecane, n-hexadecane, n-octadecane, andmixtures thereof.

According to another detailed feature of the invention, the gellingagent may be at least one saturated olefin rubber.

According to another detailed feature of the invention, the gellingagent may be at least one hydrogenated styrenic block copolymer.

According to another detailed feature of the invention, the gellingagent may be at least one styrene-ethylene-butylene-styrene tri-blockcopolymer.

According to another detailed feature of the invention, the gellingagent may be at least one high molecular weightstyrene-ethylene-butylene-styrene tri-block copolymer with astyrene:rubber ratio in the range of about 30:70 to 33:67% by weight.

According to another detailed feature of the invention, the phase-changematerial may be n-tetradecane, and the gelling agent may be a highmolecular weight styrene-ethylene-butylene-styrene tri-block copolymerwith a styrene:rubber ratio in the range of about 30:70 to 33:67% byweight.

According to another detailed feature of the invention, the gellingagent may constitute up to about 10%, by weight, of the gel, preferablyless than 6%, by weight, of the gel, with the phase-change materialconstituting the remainder of the gel.

According to another detailed feature of the invention, the temperatureat which the phase-change material and the gelling agent are mixedtogether may be in the range of about 40° C. to about 55° C.

According to another detailed feature of the invention, the gellingagent may be at least one styrene-ethylene-propylene-styrene tri-blockcopolymer.

According to another detailed feature of the invention, the gellingagent may be at least one high molecular weightstyrene-ethylene-propylene-styrene tri-block copolymer with astyrene:rubber ratio in the range of about 20:80% by weight.

According to another detailed feature of the invention, the thermalexchange implement container may be a flexible pouch.

According to another detailed feature of the invention, the thermalexchange implement container may be a rigid bottle.

According to another aspect of the invention, a novel method ofpreparing a thermal exchange implement is provided, the methodcomprising the steps of (a) providing a phase-change material; (b)providing a gelling agent; (c) mixing the phase-change material and thegelling agent at a first temperature at which the phase-change materialis in a liquid state and which is below the flash point of thephase-change material and at which the mixture is not a viscoelasticliquid, whereby a non-homogenous mixture is produced; (d) then,depositing the non-homogeneous mixture in a thermal exchange implementcontainer; (e) then, while the non-homogeneous mixture is in the thermalexchange implement container, heating the non-homogeneous mixture to asecond temperature that is below the flash point of the phase-changematerial and at which the non-homogeneous mixture forms a viscoelasticliquid; and (f) then, while the viscoelastic liquid is in the thermalexchange implement container, cooling the viscoelastic liquid to roomtemperature.

According to a detailed feature of the invention, the phase-changematerial may be at least one organic phase-change material.

According to another detailed feature of the invention, the at least oneorganic phase-change material may be at least one compound selected fromthe group consisting of n-alkanes, fatty acid esters, fatty alcohols,and fatty acids.

According to another detailed feature of the invention, the at least oneorganic phase-change material may be one or more compounds selected fromthe group consisting of n-tetradecane, n-hexadecane, n-octadecane, andmixtures thereof.

According to another detailed feature of the invention, the gellingagent may be at least one saturated olefin rubber.

According to another detailed feature of the invention, the gellingagent may be at least one hydrogenated styrenic block copolymer.

According to another detailed feature of the invention, the gellingagent may be at least one styrene-ethylene-butylene-styrene tri-blockcopolymer.

According to another detailed feature of the invention, the gellingagent may be at least one high molecular weightstyrene-ethylene-butylene-styrene tri-block copolymer with astyrene:rubber ratio in the range of about 30:70 to 33:67% by weight.

According to another detailed feature of the invention, the phase-changematerial may be n-hexadecane, and the gelling agent may be a highmolecular weight styrene-ethylene-butylene-styrene tri-block copolymerwith a styrene:rubber ratio in the range of about 30:70 to 33:67% byweight.

According to another detailed feature of the invention, the phase-changematerial may be a mixture of n-tetradecane and n-hexadecane, and thegelling agent may be a high molecular weightstyrene-ethylene-butylene-styrene tri-block copolymer with astyrene:rubber ratio in the range of about 30:70 to 33:67% by weight.

According to another detailed feature of the invention, the gellingagent may constitute up to about 10%, by weight, of the gel, preferablyless than 6%, by weight, of the gel, with the phase-change materialconstituting the remainder of the gel.

According to another detailed feature of the invention, the gellingagent may be at least one styrene-ethylene-propylene-styrene tri-blockcopolymer.

According to another detailed feature of the invention, the gellingagent may be at least one high molecular weightstyrene-ethylene-propylene-styrene tri-block copolymer with astyrene:rubber ratio in the range of about 20:80% by weight.

According to another detailed feature of the invention, where thephase-change material is a liquid at room temperature, theabove-described step of mixing the phase-change material and the gellingagent may take place at room temperature, i.e., at a temperature in therange of about 15° C. to about 30° C. or, more specifically, at atemperature in the range of about 19° C. to about 25° C.

According to another detailed feature of the invention, after the mixingstep and before the heating step, the non-homogeneous mixture may beallowed to rest for a period of time, during which time the gellingagent may swell.

According to another detailed feature of the invention, the restingperiod may be in the range of about 30 minutes to about 72 hours andpreferably may be in the range of about 16 hours to 20 hours.

According to another detailed feature of the invention, after thephase-change material and the gelling agent have been mixed to form anon-homogeneous mixture, the non-homogeneous mixture may be placed in athermal exchange implement container, and the heating, cooling andoptional resting steps may thereafter be performed on thenon-homogeneous mixture while within the thermal exchange implementcontainer.

According to another detailed feature of the invention, the temperatureat which the viscoelastic liquid is formed may be between about 40° C.and about 80° C., preferably between about 45° C. and about 65° C., andthe heating step may comprise heating to a temperature between about 40°C. and about 80° C., preferably between about 45° C. and about 65° C.

According to another detailed feature of the invention, the step ofheating the non-homogeneous mixture from the first temperature to thesecond temperature may comprise a ramp phase in which the temperature isgradually raised from the first temperature to the second temperatureand a constant (or soak) phase in which the temperature is maintained atthe second temperature.

According to another detailed feature of the invention, the ramp phasemay range from a minimum ramp rate of about 0.025° C./minute to amaximum ramp rate of about 2.5° C./minute, with a preferred ramp ratebeing in the range of about 0.15° C./minute to about 0.30° C./minute.

According to another detailed feature of the invention, the constant (orsoak) phase may range from a minimum of about 0.5 hours to a maximum ofabout 20 hours, with a preferred range of about 6 hours to about 16hours.

According to another detailed feature of the invention, the step ofcooling the viscoelastic liquid to room temperature may take placesimply by allowing the viscoelastic liquid to cool at room temperatureor may take place using cooling materials and/or equipment.

According to another detailed feature of the invention, the cooling stepmay be performed with cooling equipment and may involve a ramping downof temperature at a rate complementary to that described above for theramp phase of the heating step. In other words, the ramping down oftemperature during the cooling step may range from a minimum ramp downrate of about 0.025° C./minute to a maximum ramp down rate of about 2.5°C./minute, with a preferred ramp down rate being in the range of about0.15° C./minute to about 0.30° C./minute.

According to another detailed feature of the invention, the thermalexchange implement container may be a flexible pouch.

According to another detailed feature of the invention, the thermalexchange implement container may be a rigid bottle.

Additional objects, as well as features and advantages, of the presentinvention will be set forth in part in the description which follows,and in part will be obvious from the description or may be learned bypractice of the invention. In the description, reference is made to theaccompanying drawings which form a part thereof and in which is shown byway of illustration various embodiments for practicing the invention.The embodiments will be described in sufficient detail to enable thoseskilled in the art to practice the invention, and it is to be understoodthat other embodiments may be utilized and that structural changes maybe made without departing from the scope of the invention. The followingdetailed description is, therefore, not to be taken in a limiting sense,and the scope of the present invention is best defined by the appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are hereby incorporated into andconstitute a part of this specification, illustrate various embodimentsof the invention and, together with the description, serve to explainthe principles of the invention. In the drawings wherein like referencenumerals represent like parts:

FIG. 1 is a front view, broken away in part, of a first embodiment of athermal exchange implement for use in maintaining atemperature-sensitive material within a desired temperature range, thethermal exchange implement being constructed according to the teachingsof the present invention;

FIG. 2 is a front view, broken away in part, of a second embodiment of athermal exchange implement for use in maintaining atemperature-sensitive material within a desired temperature range, thethermal exchange implement being constructed according to the teachingsof the present invention;

FIGS. 3 and 4 are front perspective and top perspective views,respectively, of the mixing setup used in Examples 1 through 4 and inComparative Example 1;

FIG. 5 is a photo of a quantity of the gel prepared in Example 1;

FIG. 6 is a photo of the gel prepared in Example 6;

FIG. 7 is a photo of the gel prepared in Example 7;

FIG. 8 is a photo of the gel prepared in Example 8;

FIG. 9 is a photo of the gel prepared in Example 9; and

FIG. 10 is a photo of the thermal exchange implement prepared in Example13.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed, in part, at a gel comprising aphase-change material (PCM) and a gelling agent. The present inventionis also directed, in part, at a method of preparing the aforementionedgel. The present invention is additionally directed, in part, at athermal exchange implement comprising the combination of theaforementioned gel and a container holding a quantity of the gel. Thepresent invention is further directed, in part, at a method of preparingthe aforementioned thermal exchange implement.

The phase-change material of the present invention may include, but isnot limited to, one or more organic phase-change materials. The one ormore organic phase-change materials may include, but are not limited to,one or more of the following: n-alkanes, fatty acid esters, fattyalcohols, and fatty acids.

Examples of n-alkanes suitable for use as the phase-change material mayinclude, but are not limited to, n-tetradecane (n-TD), which has a phasechange temperature of about 5° C.; n-hexadecane (n-HD), which has aphase change temperature of about 17° C.; and n-octadecane (n-OD), whichhas a phase change temperature of about 28° C. Examples of n-alkanessuitable for use as the phase-change material may also include mixturesof two or more n-alkanes, such as mixtures of n-tetradecane andn-hexadecane, mixtures of n-hexadecane and n-octadecane, etc. Where, forexample, the phase-change material is a mixture of two or more n-alkanesselected from the group consisting of n-tetradecane, n-hexadecane, andn-octadecane, the relative proportions of the two or more n-alkanes ofthe mixture may be adjusted in order to modify the phase changetemperature of the mixture. For example, by selecting appropriaterelative proportions of n-tetradecane, n-hexadecane, and/orn-octadecane, one can tailor the phase change temperature of a mixturethereof to a desired phase change temperature lying within a range ofabout 2° C. to about 28° C. or, more specifically, lying within a rangeof about 2° C. to about 8° C. or within a range of about 15° C. to about28° C. For example, a mixture containing about 3.5% by weightn-hexadecane and about 96.5% by weight n-tetradecane has a phase changetemperature of about 3° C., and a mixture containing about 38.2% byweight n-tetradecane and about 61.8% by weight n-hexadecane has a phasechange temperature of about 7° C.

Examples of fatty acid esters suitable for use as the phase-changematerial may include, but are not limited to, methyl esters, which mayinclude lauric acid methyl ester (i.e., methyl laurate), myristic acidmethyl ester (i.e., methyl myristate), and mixtures thereof. Examples offatty alcohols suitable for use as the phase-change material mayinclude, but are not limited to, decyl alcohol (i.e., 1-decanol),dodecyl alcohol (i.e., 1-dodecanol), and mixtures thereof. Examples offatty acids suitable for use as the phase-change material may include,but are not limited to, ricinoleic acid, caprylic acid, and mixturesthereof.

The gelling agent of the present invention may include, but is notlimited to, one of the following or combinations of the following:organic gelling agents; organometallic gelling agents, such as, but notlimited to, alkaline or alkaline earth soaps; and inorganic gellingagents, such as, but not limited to, fumed silica (hydrophobic andhydrophilic) and bentonite clay with and without a polar activator. Ofthe aforementioned gelling agents, organic gelling agents are preferred.The aforementioned organic gelling agents may include, for example,polyamide-polyether copolymers and saturated olefin rubbers, with thelatter being preferred. Examples of such saturated olefin rubbers mayinclude hydrogenated styrenic block copolymers (HSBC), such as, but notlimited to, the copolymers commercially available from Kraton PolymersLLC (Houston, Tex.) as the Kraton G, SEBS/SEP, EP and ERS families ofcopolymers, as well as the copolymers commercially available fromKuraray America, Inc. (Houston, Tex.) as the SEPTON SEP, SEPS, SEBS andSEEPS families of copolymers.

The aforementioned Kraton G copolymers are thermoplastic elastomershaving copolymer chains in a di-block, tri-block, or multi-armconfiguration. The tri-block copolymers have styrene (S) on both ends ofthe chain and a rubber (e.g., ethylene propylene (EP) or ethylenebutylene (EB)) in the middle whereas the di-block structure has styreneon only one end of the chain. For tri-block structure based gels, it isknown that the rubber segments form separate domains and that thestyrene segments lock together to form physical cross links. The keyproperties to consider, in developing gels using SEBS and SEPScopolymers, include styrene content, molecular weight, tri-block vs.di-block, and end-use temperature. For a given concentration ofcopolymer, flow resistance is increased by increasing styrene content,increasing molecular weight, using tri-block structures and using lowertemperatures.

In addition to including a phase-change material and a gelling agent,the gel of the present invention may additionally include a nominalamount of a dye, which may be used to give the gel a desired and/ordistinctive color. In this manner, for example, gels whose respectivephase-change materials possess different phase change temperatures mayeach be dyed a different color.

As will be discussed further below, the gel of the present invention maybe prepared by at least two different techniques. According to a firstgel-forming technique, the phase-change material and the gelling agentare first mixed at an intermediate temperature that is above roomtemperature but is below the flash point of the phase-change materialand at which the gelling agent partially, but not completely, dissolvesin the phase-change material, whereby a non-homogeneous mixture isproduced. Thereafter, the non-homogeneous mixture is cooled to roomtemperature. According to a second gel-forming technique, thephase-change material and the gelling agent are mixed at a temperatureat which the phase-change material is in a liquid state and which isbelow the flash point of the phase-change material and at which themixture is not a viscoelastic liquid, whereby a non-homogenous mixtureis produced. In most instances, if the phase-change material is a liquidat room temperature, the aforementioned mixing step may take place atroom temperature. The non-homogeneous mixture is then heated to atemperature that is below the flash point of the phase-change materialand at which a viscoelastic liquid is formed. (If desired, after themixing step and prior to the heating step, the non-homogeneous mixturemay be allowed to rest for a period of time, during which time thegelling agent may swell.) The viscoelastic liquid is then cooled to roomtemperature to form the gel.

In the case of both the first technique and the second technique, thecooling step may involve simply allowing the non-homogeneous mixture tocool or may involve the use of cooling materials and/or equipment.

In accordance with the present invention, a gel comprising aphase-change material and a gelling agent preferably possesses one ormore of the following properties:

-   -   Amount of Gelling Agent: The gelling agent is preferably        commercially available in a form that allows ease of use in        manufacturing. The amount of gelling agent used should be        similar to (or below) typical refrigerant weight tolerances        (e.g. up to about 10% by weight of the gel, preferably less than        6% by weight of the gel). Furthermore, minimizing the amount of        gelling agent used is important in maximizing the latent heat        (energy absorbed or released during phase change) of the        resulting gel.    -   Gel Freeze/Thaw cycling: The gel preferably passes multiple        freeze/thaw test cycles (n=10 cycles, for example +40° C. for 6        hrs, −20° C. for 6 hrs) such that no liquid PCM separation        (syneresis) is seen during the test or after it is complete.        This is important since, as typically used, refrigerants can go        through several freeze/thaw cycles before being used and/or may        be used multiple times.    -   Gel Performance: The gelling agent should not react with the        phase-change material. In addition, the gel should have        performance equal to or exceeding conventional polyacrylic acid        (PAA)/water-based gels in terms of leakage. It is highly        desirable that the gel have a performance equal to or exceeding        conventional carboxymethyl-cellulose (CMC)/water-based gels in        terms of leakage. Ideally, the gel should not expel any liquid        PCM (no syneresis) when exposed to a 1.5 psi loading for long        time periods, such as 24 hours or more.    -   Gel Processing (mixing at room temperature): Preparation at        typical plant operating temperatures (15° C. to 30° C.) is        highly preferred. If typical plant operating temperature        preparation is used to mix the PCM and the gelling agent, and        the resulting non-homogeneous mixture is placed into its        container at room temperature, additional heating will be needed        to form a viscoelastic liquid, which will gel upon cooling back        to room temperature. Furthermore, the room temperature        non-homogeneous mixture should be able to be incorporated into        its container (gel pack, saddlebag, bottle, mat, etc.) using        conventional vertical form fill and seal (VFFS) equipment and/or        bottle filling machinery (i.e., room temperature non-homogeneous        mixture must be pump-able). An example of a vertical form fill        and seal machine is Model W-18 vertical-form-fill-seal        pouch/sachet packaging machine, which is commercially available        from Winpak Lane, Inc. (San Bernadino, Calif.).    -   Gel Processing (mixing at above room temperature): Heating (up        to flash point of PCM, which for n-tetradecane is 99° C.) while        mixing may be acceptable. The gel, once made, should be able to        be incorporated into its container (gel pack, saddlebag, bottle,        mat, etc.) using standard VFFS equipment and/or bottle filling        machinery (i.e., gel must be pump-able).    -   Gel Operating Temperature: The gel should meet its performance        requirements at typical exposure temperatures from −20° C. to        +40° C. Specifically, the gel should pass the “upside down” test        (inverted in container without any flow) over this temperature        range.    -   Gel Freeze Point Depression: Freeze point depression must be        minimized. For a 5° C. phase-change material, for example, the        gel freeze point should not go below 3° C.    -   Gel Shear Thinning: When the gel is shaken vigorously, shear        thinning is okay, but preferably the viscosity recovers quickly        (<5 minutes).

As noted above, the present invention contemplates at least twodifferent techniques by which the gel may be formed using a combinationof the phase-change material and the gelling agent. The firstgel-forming technique involves mixing the phase-change material and thegelling agent at an intermediate temperature that is above roomtemperature but is below the flash point of the phase-change materialand at which the gelling agent partially, but not completely, dissolvesin the phase-change material, whereby a non-homogeneous mixture isproduced, and then cooling the non-homogeneous mixture to roomtemperature. Such cooling may take place simply by allowing thenon-homogenous mixture to cool at room temperature or may take placeusing cooling materials and/or equipment. It is believed that, using thefirst gel-forming technique, one can obtain a gel possessing one ormore, and preferably all, of the above properties for a givenphase-change material by selecting an appropriate gelling agent, such asan SEBS or SEPS triblock copolymer having a particular styrene/rubberratio or molecular weight, and/or by adjusting mixing conditions (e.g.,temperature or mixing speed) and/or by adjusting the relativeproportions of phase-change material and gelling agent.

The second gel-forming technique involves mixing the phase-changematerial and the gelling agent at a first temperature at which thephase-change material is in a liquid state and which is below the flashpoint of the phase-change material and at which the mixture is not aviscoelastic liquid, whereby a non-homogenous mixture is produced, thenheating the non-homogeneous mixture to a second temperature that isbelow the flash point of the phase-change material and at which aviscoelastic liquid is formed, and then cooling the viscoelastic liquidto room temperature to form the gel. The temperature at which theviscoelastic liquid may be formed may be between about 40° C. and about80° C., preferably between about 45° C. and about 65° C., and theheating step may comprise heating to a temperature between about 40° C.and about 80° C., preferably between about 45° C. and about 65° C. Thestep of heating the non-homogeneous mixture may include a ramp phaseduring which the temperature is raised from the first temperature to thesecond temperature and a constant (or soak) phase during which thetemperature is maintained at the second temperature. The aforementionedramp phase may range from a minimum ramp rate of about 0.025° C./minuteto a maximum ramp rate of about 2.5° C./minute, with a preferred ramprate being in the range of about 0.15° C./minute to about 0.30°C./minute. The aforementioned constant (or soak) phase may range from aminimum of about 0.5 hours to a maximum of about 20 hours, with apreferred range of about 6 hours to about 16 hours. The step of coolingthe viscoelastic liquid to room temperature may take place simply byallowing the viscoelastic liquid to cool at room temperature or may takeplace using cooling materials and/or equipment. Preferably, the coolingstep is performed with cooling equipment and involves a ramping down oftemperature at a rate complementary to that described above for the rampphase of the heating step. In other words, the ramping down oftemperature during the cooling step may range from a minimum ramp downrate of about 0.025° C./minute to a maximum ramp down rate of about 2.5°C./minute, with a preferred ramp down rate being in the range of about0.15° C./minute to about 0.30° C./minute.

After the mixing step and prior to the heating step of the secondgel-forming technique, the non-homogenous mixture may rest for a periodof time, during which the gelling agent may swell. This resting periodmay be, for example, in the range of about 30 minutes to about 72 hours,preferably about 16 hours to about 20 hours.

It is believed that, using the second gel-forming technique, a gelpossessing most, if not all, of the above properties can be obtained.

One advantage of the second gel-forming technique, as compared to thefirst gel-forming technique, is that the second gel-forming techniqueobviates the need for equipment that is capable of both mixing thephase-change material and the gelling agent and heating thenon-homogenous mixture formed thereby. Another advantage of the secondgel-forming technique, as compared to the first gel-forming technique,is that the first gel-forming technique results in the production of agel in the mixing equipment, which may make further processing and/orpackaging of the gel more difficult.

A gel possessing many or all of the above properties may comprise one ormore n-alkanes, such as, but not limited to, n-tetradecane,n-hexadecane, n-octadecane, or mixtures thereof, as the phase-changematerial and may comprise an SEBS copolymer, such as, but not limitedto, Kraton™ G1651 copolymer (a high molecular weight SEBS tri-blockcopolymer with a styrene:rubber ratio of 30:70% by weight), Kraton™G1654 copolymer (a high molecular weight SEBS tri-block copolymer with astyrene:rubber ratio of 33:67% by weight), or Kraton™ G1660 copolymer(an SEBS tri-block copolymer with a styrene:rubber ratio of 31:69% byweight), or an SEPS copolymer, such as, but not limited to, SEPTON™S2005 copolymer (a high molecular weight SEPS tri-block copolymer with astyrene:rubber ratio of 20:80% by weight), as the gelling agent. Inparticular, where n-tetradecane is the phase-change material, and wherean SEBS tri-block copolymer like Kraton™ G1651 copolymer, Kraton™ G1654copolymer, or Kraton™ G1660 copolymer or an SEPS tri-block copolymerlike SEPTON™ S2005 copolymer is used as the gelling agent, the gellingagent preferably constitutes up to about 10%, by weight, of the gel,more preferably less than 6%, by weight, of the gel, with the balance ofthe gel being n-tetradecane (and optionally a nominal amount of dye).

Moreover, in accordance with the first gel-forming technique discussedabove, such a gel may be prepared by mixing together the phase-changematerial and the gelling agent at an “intermediate temperature” that isbelow the flash point of the phase-change material and that is elevatedrelative to room temperature but that is not so elevated that thegelling agent completely dissolves in the phase-change material. Inother words, the gelling agent preferably only partially dissolves inthe phase-change material, whereby a homogeneous solution does not form.For the Kraton™ G1651 copolymer, the intermediate temperature has beendetermined to be in the 55° C. range, for the Kraton™ G1654 copolymer,the intermediate temperature has been determined to be in the 40° C.range, for the Kraton™ G1660 copolymer, the intermediate temperature hasbeen determined to be in the 42° C. range, and for the SEPTON™ S2005copolymer, the intermediate temperature has been determined to be in the40° C. range. Such a mixture is then allowed to cool to roomtemperature.

Alternatively, in accordance with the second gel-forming techniquediscussed above, such a gel may be prepared by mixing together thephase-change material and the gelling agent at a temperature at whichthe phase change material is a liquid such that a homogeneous mixturedoes not form. If desired, the mixture may be allowed to sit to furtherswell the gelling agent. The non-homogeneous mixture may then be slowlyheated to a temperature which is below the flash point of thephase-change material such that a clear viscoelastic liquid is formed.The viscoelastic liquid may then be cooled to room temperature to formthe gel. As examples of the types of processing conditions that may beencountered for this technique to form the viscoelastic liquid and thenthe gel, the non-homogeneous mixture may be heated from its initialtemperature of 22° C.+/−3° C. to an elevated temperature of 60° C. overthe course of three hours, followed by a soak at 60° C. for 16 hours,followed by a cooling back down to 22° C.+/−3° C. over the course ofthree hours. If the non-homogeneous mixture is converted to a gelled PCMwhile in a container that is suitable for use as a thermal exchangeimplement container, a thermal exchange implement is the result. Forphase-change materials with higher phase change temperatures (i.e. +17°C., +28° C.), a thermal exchange implement may be created by heating thenon-homogeneous mixture, already in its container, from room temperatureto 65° C. over the course of 3.5 hours, followed by a soak at 65° C. for16 hours, and followed by a cooling back down to room temperature overthe course of 3.5 hours. Alternatively, a thermal exchange implement canbe made by forming the gel as described above in an open or closed moldin any desired shape and then by loading/packaging the gel into asuitable thermal exchange implement container, which loading/packagingcan be accomplished by using conventional horizontal form fill and seal(HFFS) machinery, an example of which is a Model Delta 3000 LDHorizontal Flow Wrapper machine, which is commercially available fromIlapak, Inc. (Newtown, Pa.).

Without wishing to be limited to any particular theory behind theinvention, it is believed that the SEBS or SEPS material partiallydissolves and partially swells in the phase change material, such asn-tetradecane, n-hexadecane, or mixtures thereof. The dissolution islikely based on the rubber (EB or EP) portion of the copolymer, and theswelling is likely based on the styrene (S) portion of the copolymer. Ifthe temperature is increased too much (e.g. 90° C. or more, whichapproaches the T_(g) of polystyrene), a completely clear, homogenoussolution results, consisting of both S and EB or S and EP micro-domains,which is highly undesirable. It is, therefore, very important that ahomogenous solution not form. Without being bound by theory, it ishypothesized that the styrene (S) portion of the copolymer, whenswollen, can still cross-link to allow some gel structural integrity.The rubber (EB or EP) micro-domains (T_(g) below −50° C.) give the gelits low temperature flexibility. At some (minimum) criticalconcentration (higher than the 90° C. dissolution concentration), the(SEBS or SEP S)/(n-tetradecane, n-hexadecane or mixtures thereof) formsa cohesive gel with elastic properties.

Mixing may be achieved using an overhead stirrer with a “cowles” typedisperser/mixer blade (tip speeds of 0.1 to 20 m/sec, preferably 2 to 6m/sec for the first gel-forming technique described above and 0.5 to 4.5m/sec for the second gel-forming technique described above). Such anarrangement provides a good combination of top-to-bottom flow and shearin the mixing vessel and results in good wetting of the gelling agent bythe phase-change material.

Referring now to FIG. 1, there is shown a front view, broken away inpart, of a first embodiment of a thermal exchange implement for use inmaintaining a temperature-sensitive material within a desiredtemperature range, the thermal exchange implement being constructedaccording to the teachings of the present invention and beingrepresented generally by reference numeral 11.

Thermal exchange implement 11 may comprise a sealed pouch 15. Pouch 15,which may be a flexible structure made by sealing together one or morelaminate sheets each comprising an inner polyethylene layer and at leastone outer barrier layer, may be shaped to define an interior cavity 19.A quantity of a gel 21, which may be, for example, a gel of the typedescribed above that comprises at least one phase change material, suchas n-tetradecane, n-hexadecane, or mixtures thereof, and at least onegelling agent, such as an SEBS or SEPS copolymer, may be disposed withincavity 19.

Thermal exchange implement 11 may be used similarly to a conventionalice/cold pack to keep temperature-sensitive materials within a desiredtemperature range.

Referring now to FIG. 2, there is shown a front view, broken away inpart, of a second embodiment of a thermal exchange implement for use inmaintaining a temperature-sensitive material within a desiredtemperature range, the thermal exchange device being constructedaccording to the teachings of the present invention and beingrepresented generally by reference numeral 51.

Thermal exchange implement 51 may comprise a bottle 55 and a cap 57, cap57 being securely mounted, for example, by screwing, on a neck 58 ofbottle 55. Bottle 55, which may be a rigid structure molded from apolymer, such as polyethylene, may be shaped to define an interiorcavity 59. A quantity of a gel 61, which may be, for example, a gel ofthe type described above that comprises at least one phase-changematerial, such as n-tetradecane, n-hexadecane, or mixtures thereof, andat least one gelling agent, such as an SEBS or SEPS copolymer, may bedisposed within cavity 59.

Thermal exchange implement 51 may be used similarly to thermal exchangeimplement 11 to keep temperature-sensitive materials within a desiredtemperature range.

The following examples are provided for illustrative purposes only andare in no way intended to limit the scope of the present invention:

Example 1: Gel Comprising n-Tetradecane and Kraton™ G1654 SEBS TriblockCopolymer (Mixed at 40° C.) Materials and Equipment

N-tetradecane (n-TD, C₁₄H₃₀, CAS#629-59-4, density=0.767 g/cc, purity98%+, F.P. 99° C.) was procured from a commercial supplier and was usedas supplied. Kraton™ G1654 powder (triblock SEBS co-polymerw/hydrogenated ethylene/butylene midblock, styrene:rubber ratio of33:67% by weight, density=0.91 g/cc) was procured from Kraton Polymers(Houston, Tex.) and was used as received.

Multiple experiments were completed at laboratory scale to demonstrateproof of concept for the desired mixing system. The experimentallaboratory setup is shown in FIGS. 3 and 4.

Description of Mixing Process

The mixing process was performed using an IKA RC hotplate (IKA,Wilmington, N.C.) with temperature feedback control loop, an IKA RW20(overhead stirrer) mixer (IKA, Wilmington, N.C.) and an IKA R1303(blade) stirrer (IKA, Wilmington, N.C.).

-   -   A 500 ml beaker was filled with approximately 360 grams (470 ml)        of n-tetradecane (n-TD).    -   The IKA hot plate was set to +40° C. The control loop kept the        temperature of the system at 40° C.±2° C. at all times.    -   The RW20 mixer was set to 1300 RPM (R1303 tip speed of −2.9        meters/sec), while the n-TD liquid was heated.    -   Once at temperature, Kraton™ G1654 powder (amount=18 grams, or        5% wt of n-TD) was added into the vortex of the fluid, and the        RW20 mixer was maintained at 1300 RPM for about 7 minutes.    -   As the viscosity began to increase, the RW20 mixer speed was        increased to 2400 RPM (R1303 tip speed of 5.3 m/sec), gradually        over a 2 minute time period. The RW 20 mix speed remained at        2400 RPM for an additional 10 minutes, until the viscosity was        too high for flow to occur (>10,000+ centipoise, based on RW20        capability).    -   At that time, both the RW20 mixer and the IKA hot plate were        shut off.

After cooling to room temperature, the mixture was stored for furtheranalysis. A photograph of the resulting mixture is shown in FIG. 5. Ascan be seen in FIG. 5, the resulting mixture was not a clear,homogeneous solution.

Example 2: Gel Comprising n-Tetradecane and Kraton™ G1651 SEBS TriblockCopolymer (Mixed at 55° C.)

The same procedure as in Example 1 was used, except that (1) Kraton™G1651 powder (triblock SEBS co-polymer w/hydrogenated ethylene/butylenemidblock, styrene:rubber ratio of 30:70% by weight, density=0.91 g/cc)was used in place of Kraton™ G1654 powder, (2) the control loop kept thetemperature of the system at 55° C.±1° C. at all times, and (3) the mixspeed was varied until a gel of viscosity similar to that of Example 1was obtained.

Example 3: Gel Comprising n-Tetradecane and Kraton™ G1660 SEBS TriblockCopolymer (Mixed at 42° C.)

The same procedure as in Example 1 was used, except that (1) Kraton™G1660 powder (triblock SEBS co-polymer w/hydrogenated ethylene/butylenemidblock, styrene:rubber ratio of 31:69% by weight, density=0.91 g/cc)was used in place of Kraton™ G1654 powder, (2) the control loop kept thetemperature of the system at 42° C.±2° C. at all times, and (3) the mixspeed was varied until a gel of viscosity similar to that of Example 1was obtained.

Example 4: Gel Comprising n-Tetradecane and SEPTON™ S2005 SEPS TriblockCopolymer (Mixed at 40° C.)

The same procedure as in Example 1 was used, except that (1) SEPTON™S2005 powder (triblock SEPS co-polymer w/hydrogenated ethylene/propylenemidblock, styrene:rubber ratio of 20:80% by weight, density=0.89 g/cc)was used in place of Kraton™ G1654 powder, (2) the control loop kept thetemperature of the system at 40° C.±1° C. at all times, and (3) the mixspeed was varied over a 24 minute period, until a gel of viscositysimilar to that of Example 1 was obtained.

Example 5: Testing of Various Gels (Mixed Above Room Temperature)

Gels comprising Kraton™ G1654 SEBS and n-tetradecane that were madeusing methods similar to those described in Example 1 were evaluated fortheir use as phase-change materials. Tables 1, 2 and 3 below summarizethe performance of these gels, which were prepared at differentcopolymer concentrations and mixing conditions, and also summarize theperformance of samples that did not include a gelling agent.

TABLE 1 Freeze and Thaw Phase Change Temperature Sample Material/Manufacturer Thaw PCT [C.] Freeze PCT [C.] 3% wt G1654 5.0 4.2 4% wtG1654 4.9 4.0 5% wt G1654 5.0 4.2 Average: 4.9 4.1 5% wt G1654 #1 5.64.2 5% wt G1654 #2 5.3 4.8 5% wt G1654 #3 5.7 3.9 5% wt G1654 #4 5.3 5.0Average: 5.5 4.5 Pure n-TD #1 5.6 5.0 Pure n-TD #2 5.7 5.0 Pure n-TD #35.6 5.1 Pure n-TD #4 5.7 5.0 Average: 5.6 5.0

Table 1 shows the freeze/thaw temperature test results of the n-TD PCMgel. Table 2 shows how the PCM gel performed vs. a control (612A) gelpack, filled with a water-based, synthetic polyacrylic acid (PAA) gel.Each gel pack tested was punctured with a specific hole size, andsubjected to a load of 1.5 psi for 60 seconds. The gels were alsoevaluated for both free standing (liquid n-TD) and ability to pass thefreeze/thaw test (no syneresis after 10 Freeze/Thaw cycles, each cyclecomprising a soak at −5° C. for 6 hours, followed by a soak at +15° C.for 6 hours). Table 3 is a summary of DSC test results comparing thelatent heat of the n-TD PCM gel to the parent (liquid only) n-TD used tomake the gel. As is shown in Tables 1, 2 and 3, the 5% wt Kraton™G1654/n-TD PCM met or exceeded the following criteria:

-   -   Amount of Gelling Agent: a copolymer concentration of 5% wt is        feasible    -   Gel Freeze/Thaw cycling: Showed passing results at n=10(+)        cycles    -   Gel Performance: Leakage performance exceeds synthetic        polyacrylic acid (PAA) water-based gels; the n-TD PCM gel        retained approximately 95% of the original (parent liquid n-TD)        latent heat.    -   Gel Processing: Preparation at +40° C. demonstrated, at short        mix times (15 minutes)    -   Gel Operating Temperature: The gelled PCM remains unchanged        during cycling from −20° C. to +40° C.    -   Gel Freeze Point Depression: The gelled PCM freeze/thaw points        are within specification    -   Gel Shear Thinning: The gel does not shear thin enough to        markedly lower its viscosity

TABLE 2 % wt. Freeze/ Hole size Loss Free Thaw Test % wt Mixing allowing(1.5 (liquid) Result thick- Condi- 1% wt psi for n-TD in (10 ID# enertions loss* 60 sec)* sample? cycles) 1 0% N/A 31 mil >30%  YES Pass 2 3%15 min, 40 mil 5.7% YES Fail 40° C. 3 4% 15 min, 60 mil 1.50%  YES Fail40° C.  4a  5%** 4 hrs, 60 mil 1.20%  YES Fail 22° C.  4b 5% 5 min, NANA NO*** Fail 90° C. 5 5% 5 min, 40 mil  ~2% YES Pass 40° C. 6 5% 10min, 40 mil 1.0% YES Pass 40° C. 7 5% 15 min, 81(+) mil   0.5% NO Pass40° C. 8 Control N/A 60 mil 3.6% NO Free Pass [syn- Liquid thetic] (H₂O)*612A Gel pack (6″ × 5½″ × 1″) was exposed to ~1.5 psi for 60 sec **Thismixture had 30-40% liquid n-TD as a separate layer. Performance is dueto hole “self sealing” and is not a viable approach ***Although theprocess made a very rubbery n-TD gel, it failed the F/T test

TABLE 3 SUMMARY of DSC Results: Liquid n-TD vs. Gelled (5% wt KratonTMG1654) n-TD Sample Description (Lot#, Number of AVG Onset AVG PEAK AVGLH Samples Tested) (thaw) (Deg C.) (thaw) (Deg C.) (thaw) (J/g) 98%+Pure n-TD 4.8 6.0 225.4 (Lot# 20120301), (n = 2): 5% Gelled n-TD 3.8 8.2213.5 (Lot# 20120301), (n = 3):

Comparative Example 1: Gel Comprising n-Tetradecane and “Gelled” PLUSICEA4 Rubber from PCM Products

A sample of “Gelled” PLUSICE A4 (organic PCM) Rubber was obtained fromPCM Products (Hertfordshire, UK). The sample was rotary evaporated suchthat only (solid) gelling agent remained. 5% wt of the solid gellingagent was fully dissolved in n-tetradecane, using the setup described inExample 1, at elevated temperatures (75° C.+), to make a homogeneoussolution (no transition temperature was found). After cooling to roomtemperature, the resulting gel was an opaque rubbery solid. The opaquesolid was subjected to the 10 cycle freeze/thaw test (as described inExample 5). After being subjected to the freeze/thaw test, the 5% wt“gelled” PLUSICE A4 Rubber showed a sizeable volume of liquidn-tetradecane separated from the starting material (i.e., the materialfailed the freeze/thaw test).

Example 6: Gel Comprising n-Tetradecane and Kraton™ G1654 SEBS TriblockCopolymer (Mixed at Room Temperature) Materials and Equipment

N-tetradecane (n-TD, C₁₄H₃₀, CAS#629-59-4, density=0.767 g/cc, purity98%+, F.P. 99° C.) was procured from a commercial supplier and then dyedgreen by applicant. Kraton™ G1654 powder (triblock SEBS co-polymerw/hydrogenated ethylene/butylene midblock, styrene:rubber ratio of33:67% by weight, density=0.91 g/cc) was procured from Kraton Polymers(Houston, Tex.) and was used as received.

Multiple experiments were completed at laboratory scale to demonstrateproof of concept for the mixing system at room temperature. Theexperimental laboratory setup was similar to that shown in FIGS. 3 and4, the principal differences being that the liquid height was 7.1 cm,instead of 8.6 cm, the blade diameter was 5.0 cm, instead of 4.2 cm, theblade height was 3.2 cm, instead of 3.0 to 3.5 cm, and the edge distancewas 4.3 cm, instead of 3.5 cm.

Description of Mixing/Thermal Cycling Process

The mixing was performed using an IKA RW20 (overhead stirrer) mixer anda 2″ diameter cowles blade.

-   -   A 500 ml beaker was filled with approximately 300 grams (400 ml)        of dyed n-tetradecane phase-change material at room temperature.    -   The RW20 mixer was set to 600 RPM (tip speed of −1.2        meters/sec), and Kraton™ G1654 powder (amount=15 grams, or 5% wt        of the dyed phase-change material) was added into the vortex of        the fluid, and the RW20 mixer was maintained at 600 RPM for        about 15 minutes.    -   The RW20 mixer speed was increased to 800 RPM (tip speed of 2.1        m/sec), after 15 minutes and remained at 800 RPM for an        additional 5 minutes, until the mixture was visibly consistent        throughout its volume. The mixing temperature was maintained at        22° C.+/−2° C. at all times.    -   After a total elapsed time of 20 minutes, the RW20 mixer was        shut off.    -   The resulting product was allowed to sit at 22° C.+/−3° C. for        20 hours, such that the polymer (G1654) rich portion of the        non-homogeneous mixture visibly showed additional swelling.    -   At the 20 hour mark, the non-homogeneous mixture was poured into        an 8″×8″ PYREX® glass pan and immediately subjected to the        following thermal cycle: Ramp from 22° C. to 60° C. in 3 hours,        60° C. soak for 16 hours, cool from 60° C. to 22° C. in 3 hours.        The thermal cycle temperature was maintained within +/−1° C. of        set point at all times.

After cooling to room temperature, the gel was stored for furtheranalysis. A photograph of the resulting gel, which is a tough,transparent, rubbery elastic solid, is shown in FIG. 6.

Example 7: Gel Comprising n-Hexadecane and Kraton™ G1654 SEBS TriblockCopolymer (Mixed at Room Temperature)

N-hexadecane (n-HD, C₁₆H₃₄, CAS#544-76-3, density=0.773 g/cc, purity94%+, F.P. 135° C.) was procured from a commercial supplier and then wasdyed orange by applicant. Kraton™ G1654 powder (triblock SEBS co-polymerw/hydrogenated ethylene/butylene midblock, styrene:rubber ratio of33:67% by weight, density=0.91 g/cc) was procured from Kraton Polymers(Houston, Tex.) and was used as received. The gelling agent andphase-change material were subjected to an identical mixing process asdescribed in Example 6. The thermal cycling process was modified asfollows: Ramp from 22° C. to 65° C. in 3.5 hours, 65° C. soak for 16hours, cool from 65° C. to 22° C. in 3.5 hours. After cooling to roomtemperature, the gel was stored for further analysis. A photograph ofthe resulting gel, which is a tough, transparent, rubbery elastic solid,is shown in FIG. 7.

Example 8: Gel Comprising n-Tetradecane/n-Hexadecane Mixture and Kraton™G1654 SEBS Triblock Copolymer (Mixed at Room Temperature)

N-tetradecane and n-hexadecane were procured from commercial suppliers.Applicant combined the n-tetradecane and n-hexadecane in appropriateamounts to yield a phase change composition having a phase changetemperature of about 3° C., which phase change composition was then dyedpurple by applicant. Kraton™ G1654 powder (triblock SEBS co-polymerw/hydrogenated ethylene/butylene midblock, styrene:rubber ratio of33:67% by weight, density=0.91 g/cc) was procured from Kraton Polymers(Houston, Tex.) and was used as received. The gelling agent and thephase change composition were subjected to identical mixing and thermalcycling processes as described in Example 6. After cooling to roomtemperature, the gel was stored for further analysis. A photograph ofthe resulting gel, which is a tough, transparent, rubbery elastic solid,is shown in FIG. 8.

Example 9: Gel Comprising n-Tetradecane/n-Hexadecane Mixture and Kraton™G1654 SEBS Triblock Copolymer (Mixed at Room Temperature)

N-tetradecane and n-hexadecane were procured from commercial suppliers.Applicant combined the n-tetradecane and n-hexadecane in appropriateamounts to yield a phase change composition having a phase changetemperature of about 7° C., which phase change composition was then dyedlight blue by applicant. Kraton™ G1654 powder (triblock SEBS co-polymerw/hydrogenated ethylene/butylene midblock, styrene:rubber ratio of33:67% by weight, density=0.91 g/cc) was procured from Kraton Polymers(Houston, Tex.) and was used as received. The gelling agent and thephase change composition were subjected to identical mixing and thermalcycling processes as described in Example 6. After cooling to roomtemperature, the gel was stored for further analysis. A photograph ofthe resulting gel, which is a tough, transparent, rubbery elastic solid,is shown in FIG. 9.

Example 10: Gel Comprising n-Tetradecane and Kraton™ G1651 SEBS TriblockCopolymer (Mixed at Room Temperature)

The same procedure as in Example 6 was used, except that (1) Kraton™G1651 powder (triblock SEBS co-polymer w/hydrogenated ethylene/butylenemidblock, styrene:rubber ratio of 30:70% by weight, density=0.91 g/cc)was used in place of Kraton™ G1654 powder and (2) the non-homogeneousmixture was subjected to the thermal cycle without being removed fromthe 500 ml beaker in which it was mixed. After the thermal cycle wascompleted, a gel of viscosity similar to that of Example 6 was obtained.

Example 11: Gel Comprising n-Tetradecane and Kraton™ G1660 SEBS TriblockCopolymer (Mixed at Room Temperature)

The same procedure as in Example 6 was used, except that (1) Kraton™G1660 powder (triblock SEBS co-polymer w/hydrogenated ethylene/butylenemidblock, styrene:rubber ratio of 31:69% by weight, density=0.91 g/cc)was used in place of Kraton™ G1654 powder and (2) the non-homogeneousmixture was subjected to the thermal cycle without being removed fromthe 500 ml beaker in which it was mixed. After the thermal cycle wascompleted, a gel of somewhat reduced viscosity compared to that ofExample 6 was obtained.

Example 12: Gel Comprising n-Tetradecane and SEPTON™ S2005 SEPS TriblockCopolymer (Mixed at Room Temperature)

The same procedure as in Example 6 was used, except that (1) SEPTON™S2005 powder (triblock SEPS co-polymer w/hydrogenated ethylene/propylenemidblock, styrene:rubber ratio of 20:80% by weight, density=0.89 g/cc)was used in place of Kraton™ G1654 powder and (2) the non-homogeneousmixture was subjected to the thermal cycle without being removed fromthe 500 ml beaker in which it was mixed. After the thermal cycle wascompleted, a gel of viscosity similar to that of Example 6 was obtained.

Example 13: Thermal Exchange Implement Comprising n-Tetradecane andKraton™ G1654 SEBS Triblock Copolymer, in a Flexible Pouch (Mixed atRoom Temperature)

The same procedure as in Example 6 was used, except that (1) the beakersize was increased to 2000 ml and the batch size was increased to 1600ml; (2) the mixing process was repeated to make 2.5 gallons of thenon-homogeneous mixture; (3) the non-homogeneous mixture was stored in a5 gallon container for 16 hours prior to being used; and (4) the 2.5gallons of non-homogeneous mixture was run through a conventional VFFSmachine such that 11 of Cold Chain Technologies, Inc.'s part number732M16 flexible pouch saddlebags were filled. As they were filled withthe non-homogeneous mixture, each individual pouch was sealed using theproper VFFS settings of pressure, temperature and time. All sealedflexible pouches were subjected to the thermal cycle described inExample 6. After cooling to room temperature, the gel-containingflexible pouches (i.e., thermal exchange implements) were stored forfurther analysis. A photograph of a single such thermal exchangeimplement, measuring 7″×4″×½″, is shown in FIG. 10.

Example 14: Gel Comprising n-Tetradecane and 10% by Weight Kraton™ G1654SEBS Triblock Copolymer (Mixed at Room Temperature)

The same procedure as in Example 6 was used except that (1) the RW20mixer was set to 1200 RPM and 30 grams (or 10% wt of n-tetradecane) wasadded into the vortex of the fluid and (2) the RW20 mixer speed wasincreased to 1600 RPM after 15 minutes and remained at that speed for anadditional 5 minutes (until the mixture was visibly consistentthroughout its volume). The resulting non-homogeneous mixture wasallowed to sit, and was then subjected to the thermal cycle shown inExample 6. After being cooled to room temperature, the gel was a verytough, translucent, rubbery elastic solid.

Example 15: Evaluation of CarboxyMethyl-Cellulose (CMC) Hydro-Gel BasedRefrigerants (P/N 508A)

Cold Chain Technologies, Inc. gel pack refrigerants (P/N 508A) were madeby mixing room temperature plant water with about 1.5% wt of CMC powderfor up to 15 minutes and pumping the mixture through a standard VFFSproduction machine, where gel packs were formed, filled and sealed usingthe proper settings of pressure, temperature and time. Individualrefrigerant gel packs, measuring 5.75″×4.5″×1″, were loaded intocorrugate cases (72 per case) and then palletized. After chemicalcrosslinking was completed (˜12 hours), the palletized product wasinspected for leaks, and when none were found, was placed intoinventory. One case of palletized 508A CMC gel pack refrigerants wastaken from inventory and the refrigerants were evaluated in freeze/thawtesting (as in Example 5) and in compression testing (as in Example 16).The results of this testing, summarized in Table 4, confirm that theG1654 based PCM gels of the present application perform equal to orbetter than their CMC-based hydrogel counterparts.

Example 16: Testing of Various Gels and Thermal Exchange Implements GelsMixed at Room Temperature

Gels comprising Kraton™ G1654 SEBS and dyed n-tetradecane and/orn-hexadecane made using methods similar to those described in Example 6were evaluated for their use as phase-change materials. Thermal exchangeimplements made using methods similar to those in Example 13 were alsoevaluated. Table 4, below, summarizes the performance of these gels andThermal Exchange Implements, which were subjected to both freeze/thawand compression testing. Specifically, each gel was subjected to a loadof 1.5 psi for 24 hours and then evaluated for syneresis (free standingliquid PCM in the sample container) as well as their ability to pass thefreeze/thaw test (no syneresis after 10 Freeze/Thaw cycles), with onecycle defined as 6 hours at −20° C., followed by 6 hours at +40° C. Asis shown in Table 4, the 5% wt Kraton™ G1654 gelling agent based PCMs,as well as the Thermal Exchange Implements, met all key criteria andperformed equal to or better than Cold Chain Technologies, Inc.'sconventional CMC-based refrigerants.

TABLE 4 Mix/Swell Cycle Free Liquid Syneresis Test F/T Test EX GellingAgent: PCM (mixing at room Thermal Cycle in Gel as (1.5 psi for (n = 10# Concentration Type temperature) (ramp/soak/ramp) made? 24 hours)*cycles) ** 6 G1654: 5% wt 5° C. 600 RPM for 22° C./60° C./22° C. NO PASSPASS 15 min, 800 3 hrs/16 hrs/3 hrs RPM for 5 min, sit for 20 hrs. 7G1654: 5% wt 17° C.  600 RPM for 22° C./65° C./22° C. NO PASS PASS 15min, 800 3.5 hrs/16 hrs/3.5 hrs RPM for 5 min, sit for 20 hrs. 8 G1654:5% wt 3° C. 600 RPM for 22° C./60° C./22° C. NO PASS PASS 15 min, 800 3hrs/16 hrs/3 hrs RPM for 5 min, sit for 20 hrs. 9 G1654: 5% wt 7° C. 600RPM for 22° C./60° C./22° C. NO PASS PASS 15 min, 800 3 hrs/16 hrs/3 hrsRPM for 5 min, sit for 20 hrs. 10 G1651: 5% wt 5° C. 600 RPM for 22°C./60° C./22° C. NO Not Not 15 min, 800 3 hrs/16 hrs/3 hrs Tested TestedRPM for 5 min, sit for 20 hrs. 11 G1660: 5% wt 5° C. 600 RPM for 22°C./60° C./22° C. NO Not Not 15 min, 800 3 hrs/16 hrs/3 hrs Tested TestedRPM for 5 min, sit for 20 hrs. 12 S2005: 5% wt 5° C. 600 RPM for 22°C./60° C./22° C. NO Not Not 15 min, 800 3 hrs/16 hrs/3 hrs Tested TestedRPM for 5 min, sit for 20 hrs. 13 G1654: 5% wt 5° C. 600 RPM for 22°C./60° C./22° C. NO PASS PASS 15 min, 800 3 hrs/16 hrs/3 hrs RPM for 5min, sit for 16 hrs. 14 G1654: 10% wt 5° C. 1200 RPM 22° C./60° C./22°C. NO PASS*** PASS for 15 min, 3 hrs/16 hrs/3 hrs 1600 RPM for 5 min,sit for 20 hrs. 15 CMC: 1.5% 0° C. Not Applicable: Not Applicable NOPASS FAIL wt (control) (Water) See Example 15 write-up *Although nosyneresis was seen, 5% wt samples did show slight permanent deformationpost test (CMC showed significant deformation) ** Samples that passedfreeze/thaw testing showed reduced mechanical properties (reducedtoughness) upon post test inspection. ***10% wt, 5° C. PCM gel subjectedto a loading of 1.5 psi for 24 hours did not exhibit any permanentdeformation.

The embodiments of the present invention recited herein are intended tobe merely exemplary and those skilled in the art will be able to makenumerous variations and modifications to it without departing from thespirit of the present invention. All such variations and modificationsare intended to be within the scope of the present invention as definedby the claims appended hereto.

1. A gel comprising a phase-change material and a gelling agent, whereinthe phase-change material is at least one n-alkane, the gel being formedby (a) mixing the phase-change material and the gelling agent at a firsttemperature at which the phase-change material is in a liquid state andwhich is below the flash point of the phase-change material and at whichthe mixture is not a viscoelastic liquid, whereby a non-homogenousmixture is produced; (b) then, heating the non-homogeneous mixture to asecond temperature that is below the flash point of the phase-changematerial and at which a viscoelastic liquid is formed; and (c) then,cooling the viscoelastic liquid to room temperature.
 2. The gel asclaimed in claim 1 wherein the at least one n-alkane is selected fromn-alkanes ranging in size from n-tetradecane to n-octadecane.
 3. The gelas claimed in claim 2 wherein the phase-change material comprisesn-tetradecane, n-hexadecane, n-octadecane, and mixtures thereof.
 4. Thegel as claimed in claim 1 wherein the gelling agent is selected from thegroup consisting of at least one styrene-ethylene-butylene-styrene(SEBS) tri-block copolymer, at least onestyrene-ethylene-propylene-styrene (SEPS) tri-block copolymer, andmixtures thereof.
 5. The gel as claimed in claim 4 wherein the gellingagent is at least one high molecular weightstyrene-ethylene-butylene-styrene tri-block copolymer with astyrene:rubber ratio of about 30:70 to 33:67 by weight.
 6. The gel asclaimed in claim 4 wherein the gelling agent is at least one highmolecular weight styrene-ethylene-propylene-styrene tri-block copolymerwith a styrene:rubber ratio of about 20:80 by weight.
 7. The gel asclaimed in claim 1 wherein the gelling agent constitutes up to about10%, by weight, of the gel.
 8. The gel as claimed in claim 1 wherein thegelling agent constitutes up to about 10%, by weight, of the gel, withthe phase-change material and, optionally, a dye constituting theremainder of the gel.
 9. The gel as claimed in claim 1 wherein the firsttemperature is in the range of about 15° C. to about 30° C.
 10. The gelas claimed in claim 1 wherein the first temperature is in the range ofabout 19° C. to about 25° C.
 11. A method of preparing a gel, the methodcomprising the steps of: (a) providing a phase-change material, whereinthe phase-change material comprises at least one n-alkane; (b) providinga gelling agent; (c) mixing the phase-change material and the gellingagent at a first temperature at which the phase-change material is in aliquid state and which is below the flash point of the phase-changematerial and at which the mixture is not a viscoelastic liquid, wherebya non-homogenous mixture is produced; (d) then, heating thenon-homogeneous mixture to a second temperature that is below the flashpoint of the phase-change material and at which a viscoelastic liquid isformed; and (e) then, cooling the viscoelastic liquid to roomtemperature.
 12. The method as claimed in claim 11 wherein the at leastone n-alkane is selected from n-alkanes ranging in size fromn-tetradecane to n-octadecane.
 13. The method as claimed in claim 11wherein the gelling agent is selected from the group consisting of atleast one styrene-ethylene-butylene-styrene (SEBS) tri-block copolymer,at least one styrene-ethylene-propylene-styrene (SEPS) tri-blockcopolymer, and mixtures thereof.
 14. The method as claimed in claim 13wherein the gelling agent is at least one high molecular weightstyrene-ethylene-butylene-styrene tri-block copolymer with astyrene:rubber ratio of about 30:70 to 33:67 by weight.
 15. The methodas claimed in claim 13 wherein the gelling agent is at least one highmolecular weight styrene-ethylene-propylene-styrene tri-block copolymerwith a styrene:rubber ratio of about 20:80 by weight.
 16. The method asclaimed in claim 11 wherein the gelling agent constitutes up to about10%, by weight, of the gel.
 17. The method as claimed in claim 11wherein the first temperature is in the range of about 15° C. to about30° C.
 18. The method as claimed in claim 11 wherein the firsttemperature is in the range of about 19° C. to about 25° C.
 19. Themethod as claimed in claim 11 wherein the phase-change material is atleast one n-alkane ranging in size from n-tetradecane to n-octadecaneand wherein the gelling agent is at least one high molecular weightstyrene-ethylene-butylene-styrene tri-block copolymer with astyrene:rubber ratio of about 30:70 to 33:67 by weight.
 20. The methodas claimed in claim 19 wherein the phase-change material isn-tetradecane.
 21. The method as claimed in claim 11 further comprising,after the mixing step and before the heating step, the step of allowingthe non-homogenous mixture to rest.
 22. The method as claimed in claim11 wherein the first temperature is in the range of about 19° C. toabout 25° C. and wherein the second temperature is in the range of about45° C. to about 60° C.
 23. The method as claimed in claim 11 whereinsaid heating step comprises a ramp phase in which the temperature isramped from the first temperature to the second temperature and aconstant phase in which the temperature is maintained at the secondtemperature.
 24. The method as claimed in claim 23 wherein the rampphase ranges from a rate of about 0.025° C./minute to about 2.5°C./minute.
 25. The method as claimed in claim 23 wherein the constantphase ranges from about 0.5 hours to about 20 hours.
 26. The method asclaimed in claim 11 wherein said cooling step comprises cooling at arate of about 0.025° C./minute to about 2.5° C./minute.
 27. A thermalexchange implement comprising the gel of claim 1 and a container holdinga quantity of the gel.
 28. The thermal exchange implement as claimed inclaim 27 wherein the container is a flexible pouch.
 29. The thermalexchange implement as claimed in claim 27 wherein the container is arigid bottle.
 30. A method of preparing a thermal exchange implement,the method comprising the steps of: (a) providing a phase-changematerial; (b) providing a gelling agent; (c) providing a thermalexchange implement container; (d) mixing the phase-change material andthe gelling agent at a first temperature at which the phase-changematerial is in a liquid state and which is below the flash point of thephase-change material and at which the mixture is not a viscoelasticliquid, whereby a non-homogenous mixture is produced; (e) then, heatingthe non-homogeneous mixture to a second temperature that is below theflash point of the phase-change material and at which thenon-homogeneous mixture forms a viscoelastic liquid; and (f) then,cooling the viscoelastic liquid to room temperature; (g) wherein theheating and cooling steps are performed while the non-homogeneousmixture is disposed within the thermal exchange implement container.